Earthquake in Illinois could portend an emerging threat

[megimoo]

Earthquake in Illinois Could Portend an Emerging Threat

"Better get ready Sara for a good shaking !"

"These fault lines extend all through the Wabash Valley fault and into Missouri's New Madras !"
Obermeir and others have found disturbed sediments from previous earthquakes along the fault with estimated magnitudes of about 7 on the Richter scale over the past several thousand years.

April 24, 2008 -- To the surprise of many, the earthquake on April 18, 2008, about 120 miles east of St. Louis, originated in the Wabash Valley Fault and not the better-known and more-dreaded New Madrid Fault in Missouri's bootheel.

Map of the region surrounding Memphis, TN. Darker orange area is covered by thick sediments called the Mississippi embayment, that affect how the ground shakes during earthquakes. White lines indicate likely locations of faults, and black dots show the locations of earthquakes since the mid-1970s.

The concern of Douglas Wiens, Ph.D., and Michael Wysession, Ph.D., seismologists at Washington University in St. Louis, is that the New Madrid Fault may have seen its day and the Wabash Fault is the new kid on the block.

The earthquake registered 5.2 on the Richter scale and hit at 4:40 a.m. with a strong aftershock occurring at approximately 10:15 a.m. that morning, followed by lesser ones in subsequent days. The initial earthquake was felt in parts of 16 states.

"I think everyone's interested in the Wabash Valley Fault because a lot of the attention has been on the New Madrid Fault, but the Wabash Valley Fault could be the more dangerous one, at least for St. Louis and Illinois," said Wiens, professor of earth and planetary sciences in Arts & Sciences.

"The strongest earthquakes in the last few years have come from the Wabash Valley Fault, which needs more investigation."

Wiens said that seismologist Robert Hermann of Saint Louis University, Gary Pavils of Indiana University, and several geologists including Steven Obermeir of the U.S. Geological Survey (USGS), have made studies of the Wabash Valley Fault. Pavils also has run a dense local array of stations and recorded many very small earthquakes at the Wabash Valley Fault. Hermann has studied the 1968 magnitude 5.5 earthquake, the largest ever recorded there. Obermeir and others have found disturbed sediments from previous earthquakes along the fault with estimated magnitudes of about 7 on the Richter scale over the past several thousand years.
http://news-info.wustl.edu/tips/page/normal/11630.html

[megimoo]

Scientist: New fault could mean major Ark. temblor

LITTLE ROCK, Ark. – A previously unknown fault in eastern Arkansas could trigger a magnitude 7 earthquake with an epicenter near a major natural gas pipeline, a scientist said Wednesday. Haydar Al-Shukri, the director of the Arkansas Earthquake Center at the University of Arkansas at Little Rock, said the fault is separate from the New Madrid fault responsible for a series of quakes in 1811-12 that caused the Mississippi River to flow backward.

http://news.yahoo.com/s/ap/20090122/ap_on_re_us/arkansas_earthquakes

[megimoo]

Scientists Explain Source Of Mysterious Tremors Emanating From Fault Zones

Science Daily — Tiny tremors and temblors recently discovered in fault zones from California to Japan are generated by slow-moving earthquakes that may foreshadow catastrophic seismic events, according to scientists at Stanford University and the University of Tokyo. In a study published in the March 15 issue of the journal Nature, the research team focused on weak seismic signals known as "non-volcanic tremor" and "low-frequency earthquakes," which seismologists say may be useful in forecasting the likelihood of potentially destructive mega-quakes of magnitude 8 or higher.

"Non-volcanic tremor is a weak shaking of the Earth that was discovered about five years ago said Gregory C. Beroza, professor of geophysics at Stanford and co-author of the Nature study. tremor shakes the Earth for hours, days or even weeks at a time."

"It's often accompanied by low-frequency earthquakes [LFEs]--small temblors of magnitude 1 or 2. Some people believe that LFEs and tremor are separate phenomena, but what we've shown in this paper is that they are actually the same thing. Tremor is simply a swarm of low-frequency earthquakes, but rather than happening quickly and impulsively like ordinary earthquakes, tremor shakes the Earth for hours, days or even weeks at a time."

Destructive zones

To date, non-volcanic tremor and LFEs have been found primarily in subduction zones--seismically active faults where two tectonic plates meet and one plate constantly dives beneath the other. The most destructive earthquakes ever recorded have occurred in subduction zones, in places such as Chile, Japan, Alaska, Washington state and British Columbia. A recent example was the devastating 2004 earthquake near Sumatra, where a magnitude 9.2 temblor triggered powerful tsunamis that killed more than 200,000 people.

These violent mega-thrusts occur every 100 to 600 years, depending on the location. Recent studies suggest that giant quakes, which form at relatively shallow depths, are preceded by a series of much deeper events called slow (or silent) earthquakes, which displace the ground without shaking it. A slow earthquake can last days, months or years without being felt at the surface.

"In Japan, the deep section of the fault where slow earthquakes form is particularly significant, because it lies next to the shallower locked portion of the fault, where big quakes periodically strike," Beroza said. "So each time a slow earthquake happens, it adds stress to the locked section and increases the likelihood of a magnitude 8 mega-thrust. Therefore, knowing when a slow earthquake has occurred could be useful in seismic hazard forecasting."

Tremor trauma

But detecting slow quakes is a difficult task, he added. That's one reason why seismologists were particularly excited by the recent discovery of non-volcanic tremor and LFEs in the subduction zone near Shikoku, Japan.

http://www.sciencedaily.com/releases/2007/03/070314153216.htm

[SarasotaRepub]

Thanks megi!!!

You're just a ray of sunshine today. :mad:

SLW and I better move to SugarLoaf Key....:D

[megimoo]

Thanks megi!!!

You're just a ray of sunshine today. :mad:

SLW and I better move to SugarLoaf Key....:D
News like this keeps your blood moving and keeps you young.The safest place from earthquakes is somewhere along the eastern slope of the Appalachian highlands down through Georgia and Pennsylvania.The tectonic plates along the east coast are separating underwater along the mid Atlantic ridge so there is no subduction zone and therefore no earthquakes to speak of .

[SarasotaRepub]

News like this keeps your blood moving and keeps you young.The safest place from earthquakes is somewhere along the eastern slope of the Appalachian highlands down through Georgia and Pennsylvania.The tectonic plates along the east coast are separating underwater along the mid Atlantic ridge so there is no subduction zone and therefore no earthquakes to speak of .


Sure,sure...that's what the earthquakes want you to think.:D